Question

A beam PQRS is 18 m long and is simply supported at points Q and R 10m apart. Overhangs PQ and RS are 3 m and 5m respectively. A train of two point loads of 150 kN and 100 kN, 5m apart, crosses this beam from left to right with 100 kN load leading.
During the passage of the loads, the maximum and minimum reactions at support R, in kN, are respectively.

• A. 300 and -25
• B. 300 and -30
• C. 225 and -30
• D. 225 and -25

Answer 1

The correct option is B 300 and -30


Maximum reaction at support R,

$R=100\times 1.5+150\times 1=300kN$

Minimum Reaction at support R,

Case-1
When 100 kN load is at P
$\text{Reaction at, R}=-0.3\times 100$
$=-30kN$

Case-II
When 150 kN load is at P


$\text{Reaction at, R}=-0.3\times 150+100\times \frac{1}{10}\times 2$
$=-25kN$

Hence,minimum reaction = -30 kN